Effect of ‘Fluorophenylammonium’ and ‘Fluorophenethylammonium’ as Spacer on the Photo(electro)chemical and Photocatalytic Behaviour of Mixed Halide Based Layered Perovskites

Abstract Two‐dimensional lead (Pb 2+ ) based halide perovskites (2D‐PbHaPs) with a structural formula of R 2 PbX 4 (where R=organic amine and X=Cl, Br or I) represents a ‘layered’ structure, having better stability compared to three‐dimensional lead halide perovskites (3D‐PbHaPs) such as APbX 3 (where A=methylammonium and X=Cl, Br or I). The choice of ‘R’ site, which acts as a ‘spacer’ in the PbX 6 4− octahedral framework, is critical in determining the optical and electrical properties of the 2D‐PbHaP based semiconductors. In this study, two different spacers [4‐fluorophenethylammonium‐FC 6 H 4 −CH 2 −CH 2 −NH 3 + ; abbreviated as FPEA and 4‐fluorophenylammonium‐FC 6 H 4 −NH 3 + ; abbreviated as FPA] are selected as ‘R’ site of the 2D framework of ‘mixed halide’ based 2D‐PbHaP systems [(FPEA) 2 PbI 2 Br 2 and (FPA) 2 PbI 2 Br 2 )], to examine the impact of the ‘spacer’ on the optical properties, photo(electro)chemical, and photocatalytic behavior in the form of thin‐films. The thin films were having an approximate thickness of 325±25 nm. The bandgap (E BG ) and photo‐luminescence peak of (FPA) 2 PbI 2 Br 2 was observed to be red‐shifted compared to (FPEA) 2 PbI 2 Br 2 . Chronoamperometry and linear sweep voltammetry (LSV) analysis indicated a ∼100 % improvement in the photo‐current density for (FPA) 2 PbI 2 Br 2 compared to (FPEA) 2 PbI 2 Br 2 . Furthermore, the (FPA) 2 PbI 2 Br 2 based system showed better photocatalytic activity towards degradation of methylene blue and S−S coupling reactions, compared to (FPEA) 2 PbI 2 Br 2 .